In process automation technology, as well as in manufacturing automation technology, field devices are often applied for registering and/or influencing process variables. Serving for registering process variables are measuring devices, such as, for example, fill level measuring devices, flow measuring devices, pressure and temperature, measuring devices, pH-measuring devices, conductivity measuring devices, etc., which register the corresponding process variables, fill level, flow, pressure, temperature, pH-value, and conductivity, respectively. Used for influencing process variables are actuators, such as valves or pumps, via which e.g. flow of a liquid in a pipeline or fill level of a medium in a container is changed. Referred to as field devices are, in principle, all devices, which are applied near to the process and deliver, or process, process-relevant information. A large number of such field devices are available from the firm, Endress+Hauser. In connection with the invention, the term “field devices” refers, thus, to all types of measuring devices and actuators.
In modern industrial plants, field devices are, as a rule, connected via bus systems, such as, for example, a Profibus® PA, Foundation Fieldbus® or HART® bus system, with at least one superordinated control unit. The superordinated control unit can also be referred to as an object-based, management and/or configuration system for field devices. The control unit is, for example, a control system or a control unit, such as, for example, a programmable logic controller, or PLC. The PLC can be integrated, for example, into a personal computer or into a laptop. The term “device objects” refers, in connection with the present invention, to all types of electronic device descriptions. The superordinated control unit serves for process control, for process visualizing, for process monitoring, as well as for start-up and servicing of the field devices. Programs, which run self-sufficiently on superordinated units, include, for example, the operating, or servicing, tools, FieldCare of Endress+Hauser, Pactware, AMS of Fisher-Rosemount or PDM of Siemens. Operating tools, which are integrated into control system applications, include PCS7 of Siemens, Symphony of ABB and Delta V of Emerson. The terminology, “servicing of field devices”, means, especially, the configuring and parametering of field devices, however, also diagnosis for the purpose of early detecting of defects at one of the field devices or in the process.
The integration of field devices into object-based, configuration or management systems occurs via device descriptions, which care therefor, that the superordinated units can recognize and interpret the data delivered by the field devices. The device manufacturers provide device descriptions for each field device type, or for each field device type as a function of application. In order that the field devices can be integrated into different fieldbus systems, different device descriptions for the different fieldbus systems must be created. Thus, there are, to name just a few examples, HART, Fieldbus Foundation and Profibus, device descriptions.
For the purpose of creating a uniform description for field devices, Fieldbus Foundation (FF), HART Communication Foundation (HCF) and Profibus Nutzer(user)organisation (PNO) have created a uniform, electronic device description (Electronic Device Description, or EDD). The EDD is defined in the standard IEC 61804-2.
For a comprehensive servicing of field devices, moreover, particular device descriptions, so called DTMs—Device Type Managers or device managers—are obtainable. The DTMs meet the FDT—Field Device Tool—specifications. The FDT specification, representing an industrial standard, is an interface specification and was developed by the PNO, in cooperation with the ZVEI—Zentralverband Elektrotechnik-und Elektroindustrie (German Electrical and Electronics Manufacturers' Association). Current FDT specifications are obtainable from ZVEI, PNO, or the FDT Group.
Many field device manufacturers deliver along with their field devices the corresponding DTMs or device descriptions. The DTMs encapsulate all device-specific data, functions and operating rules, such as e.g. the device structure, present communication possibilities and the graphical user interface, e.g the GUI, for a certain field device or for a particular field device type.
As runtime environment, the DTMs require a frame application—here, the FDT-frame. The frame application and the corresponding DTMs permit a very comfortable access to field devices, e.g. to device parameters, measured values, diagnostic information, status information, etc., as well as permitting the invoking of special functions, which individual DTMs make available. Frame application and DTMs form together an object-based management or configuration system for field devices. In order that the DTMs of different manufacturers correctly function in the frame application, the interfaces for frame application and for all the rest of the DTMs must be clearly defined. This interface definition is referred to with the acronym FDT. The FDT technology unifies the communication interface between the field devices and the superordinated control unit. A special feature of the FDT technology is that it functions independently of the installed communication protocol as well as of the respective software environment of both the field device and the superordinated control unit. FDT enables combining any field devices via any superordinated control units with any protocols. A known FDT frame is the already mentioned product, FieldCare, of Endress+Hauser.
From the above discussion, it is clear, that the number of DTMs, or device descriptions, is very large and that the number of DTMs, based on the continually increasing device, and fieldbus, numbers, is likewise continually increasing. Often, consequently, one also speaks of a so-called DTM library. The effort, which must be expended for installation of drivers for the communication hardware, communication DTMs, field device DTMs and the software for the frame application, or the FDT servicing software, is very high.